Digital Accompaniments 1: Changing Tempos and other Transformations. This presentation by Terry B. Ewell addresses ways to change tempos in audio and MIDI files. It also addresses changes in instrumentation and methods for creating MIDI files. BDP #279,

[Music: Hummel Bassoon Concerto]

Welcome, I am Terry Ewell. This video is made during the height of COVID 19, Coronavirus, epidemic in the USA. Many music teachers are struggling with how their students can continue to perform with accompaniments at a time of social distancing or even quarantines. This video and the following two videos present solutions that I am currently employing with my students.

Now undoubtably many teachers are having accompanists record themselves and then have students practice or even produce recordings to those accompaniments. However, it is far more useful to have a MIDI files as the sources of the accompaniment rather than audio files such as those in wav, aif, or mp3 formats. If at all possible, have your accompanist record a MIDI file. This is far more useful than the audio file for accompaniment purposes. Let’s demonstrate the reasons for this.

Tempo Changes: Audio vs. MIDI

Direct recordings of acoustic piano can be unsatisfactory for several reasons. The audio quality of  pianists recording in their homes may yield poor results.
For instance, this is a recording I made with a grand piano in my home.

[musical example, Pierné Concertpiece]

Clearly this is far from studio quality.

Next, requiring the accompanist to record at multiple tempos is fatiguing. Although it is possible to change the tempos of audio files to save the pianist this effort, the results are also less than ideal. For instance, let me show you how to change tempos without altering the pitch.

Audacity is an open source software readily available that will change tempos without changing the pitch.

OK, so in order to alter the file go to effects, change tempo: “change tempo without changing pitch.” Percent, let’s do 200 percent. OK, let it process, alright. Let’s listen to this.

[musical example, Pierné Concertpiece]

However, the audio quality degrades the original file even more since each note’s sound wave is slightly clipped to create the faster tempos. Here again is the original file sample, followed by samples at tempos 62 and 92.

[musical examples, Pierné Concertpiece]

The further removed the audio file is from the original tempo the worse the quality will be.

MIDI files, however, do not suffer from the same loss of quality. Let me give an overview of how the MIDI files are created and then a demonstration of changes made to the files.

How are MIDI files created?

In the 1990s I recorded hundreds of accompaniments for my students and to share with the double reed community. Entering the data by hand would take far too long in a MIDI sequencer such as Aria Maestosa. Instead, I recorded the accompaniment at a slow tempo—one that I can sight read with reasonable accuracy. I didn’t have time and still don’t to practice each accompaniment for the hours required to master it at tempo. So, recording MIDI files at the slower tempo is the perfect solution. I set a metronome or click track when I make the recording.
For almost 20 years I have used Yamaha Clavinovas to generate the MIDI files. This could also be done with a MIDI keyboard connected to a computer and music program such as Finale.

Changing the Tempo in MIDI

There are several programs that can be used to change tempos in MIDI files. Currently I find MuseScore 3 to be the best for my purposes.

I first import the file into MuseScore. Here, for example, is a file that I was working on today for a student. Then I delete the tempo indication. I don’t know why, but just altering this tempo indication won’t make the changes. After deleting the original tempo indication I add a new indication. Add—Text—Tempo Marking. Oh, I forgot that I have to select the first note. Add—Text—Tempo Marking. Once I have the tempo marking here, I can put in the tempo that I would like to have.
Please understand that the score not correctly notated. The notation imported in here is nothing like it should appear.

[musical example, Pierné Concertpiece]

That is tediously slow, isn’t it? It says “80” here. Well, why don’t we double the speed here, 160, let’s see how that sounds.

[musical example, Pierné Concertpiece]

OK, so that might be a good practice tempo. I would take out my metronome and figure out what tempo that is while this is playing. Let’s even make it twice as fast.

[musical example, Pierné Concertpiece]

So, that is much closer to performance tempo. I can then export that to an mp3. As you can see I have some files in here and I always give the tempo marking indication in the file name so that I know what it is.

You can see here that it is very easy to export a number of different tempos, practice tempos as well as up to performance speed. This is much quicker that having to play the part over and over again. In addition, the quality of each version is the same. Here MuseScore generates mp3 files that sound just as good whatever speed they are at. That is quite different than audio files that were manipulated to get different speeds.

Instrumentation Changes in MIDI

Another great advantage to the MIDI files is that changing the instrumentation is easy. For instance, I prefer the Baroque accompaniments to have a harpsichord sound. This, for instance, is a file that I have for the Besozzi Sonata. I have some starting notes and then both the bassoon and harpsichord enter here.

[musical example: Besozzi Sonata]

OK, but let’s say I didn’t harpsichord. Let’s say I wanted something else. Go to view, mixer… and that brings up our mixer. Let’s say I wanted vibraphone to play this instead! Let’s hear how it sounds with vibraphone.

[musical example: Besozzi Sonata]

Not as good. I think I will switch that back to harpsichord. That was definitely not my preference for Baroque music. Oops, harpsichord is off of your screen but I did manage to make the change there.

So, in conclusion, if at all possible, have your accompanist record a MIDI file.  Recordings rendered as MIDI files offer the most flexibility for practice files. This is far more useful than the audio file for accompaniment purposes.

[Music: Hummel Bassoon Concerto]